The proliferation of intercity bus companies that pick up their passengers curbside has corresponded with an increase in bus accidents and fatalities, the National Transportation Safety Board said in a report released Monday.

Curbside bus companies are more than five times more likely to be involved in fatal accidents than conventional intercity bus service companies, and newcomers to the business that operate 10 or fewer buses are more likely to be in accidents, the NTSB said.

Overall, however, the federal safety agency concluded that intercity buses rarely crash and are a safer way to travel than passenger vehicles. The NTSB studied the performance of 122 bus companies, at least 71 of which provide curbside service.

“Motor coach safety, including curbside motor coach safety, is strongly influenced by the management of the carriers that own these vehicles and the drivers that operate them,” the NTSB concluded.

Sudden growth in the number of intercity buses operating since 2005, many of them curbside operators rather than those based at bus terminals, has put more buses on the road than state and federal inspectors can handle.

The report said there are 2,327 safety inspectors who are responsible for 53,097 buses. Just 878 state and local inspectors are qualified to perform full compliance reviews, which take a week or two.

The NTSB said that between April 2009 and March 2011, 8 percent of curbside carriers, 12 percent of conventional carriers and 37 percent of nonscheduled other carriers did not have inspections.

“Motorcoach safety is on the NTSB’s Most Wanted List because of the potential for high-consequence accidents like we saw in the Bronx,” said NTSB Chairman Deborah A.P. Hersman. “It’s time to recognize that traditional transportation services have morphed into new business models that challenge existing regulatory constructs.”

The NTSB report came at the request of two Democratic members of Congress from New York, Sen. Charles E. Schumer and Rep. Nydia Velazquez, after a curbside bus headed for Chinatown in New York from the Mohegan Sun Casino in Connecticut ran off a highway and split open in March, killing 15 people and injuring 18 others.

Two months later, another bus crashed on Interstate 95 in Virginia, killing four people and injuring 54. The company that operated that bus, which reportedly had been cited for driver fatigue 46 times in the two previous years, was ordered shut down. But authorities said it resumed operation under two different names within days.

“Reincarnated carriers that resume operations after getting unsatisfactory safety ratings are deliberately engaging in deceptive practices,” the NTSB report said.

Bus companies are able to change their names and keep doing business because they can hopscotch among states, which each set their own guidelines. The Federal Motor Carrier Safety Administration is seeking authority to establish those standards. The NTSB said it also should levy more substantial fines for safety violations.

“In many cases, FMCSA monetary fines for violations are too low to act as a deterrent, and motor coach carriers may view the fines as a cost of doing business,” the report said.

The NTSB said some curbside companies seek to undermine state and federal oversight by obtaining multiple Transportation Department registration numbers and operating under multiple names. That allows them to spread their record of violations or accidents among many companies so no one company appears to be performing below par.

The report said falsification of logbooks is a bigger issue with curbside carriers, who received about a quarter of all false logbook violations but made up about 2 percent of all motor coach carriers inspected.

Federal and state inspectors told the NTSB that many drivers who work for curbside bus companies lacked sufficient English-language skills to perform their jobs.

The NTSB concluded that 53 percent of the driver fitness violations lodged against curbside carriers were because of English deficiencies, compared to 11 percent among conventional carriers.

“This deficiency, although not illegal, may lead to misunderstandings and violations of FMCSA regulatory requirements,” the NTSB said.